Atorvastatin does not display an antimicrobial activity on its own nor potentiates the activity of other antibiotics against Acinetobacter baumannii ATCC17978 or A. baumannii AB030

With the current arsenal of antibiotics increasingly becoming ineffective against bacteria, there is an increasing interest in the possibility of using previously approved non-antibiotic drugs as antimicrobials. Statins have recently been investigated for their antimicrobial activity and their ability to potentially synergize with current treatment options. Atorvastatin had been shown previously to be the most promising candidate for effectivity against Acinetobacter baumannii ATCC17978. In this study, we tested atorvastatin for its activity against an extensively drug-resistant (XDR) strain A. baumannii AB030. However, our data show that atorvastatin has no effect A. baumannii AB030. Intriguingly, atorvastatin was also ineffective against our laboratory’s A. baumannii ATCC17978. This lack of atorvastatin activity against A. baumannii ATCC17978 cannot be attributed to RND efflux pumps as a strain deficient in the three most clinically relevant RND efflux systems in A. baumannii showed no change in susceptibility compared to its parent strain ATCC17978. Further, atorvastatin failed to potentiate the activity of tobramycin and ciprofloxacin. While it is not clear to us why atorvastatin is not active against A. baumannii ATCC17978 used in our study, our study shows that evaluation of compounds for their antibacterial activity should involve multiple strains to account for strain-to-strain variation.

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Cell-free supernatants produced by lactic acid bacteria reduce Salmonella population in vitro

Microbiology ◽

10.1099/mic.0.001102 ◽

2021 ◽

Vol 167 (11) ◽

Author(s):

Alberto Gonçalves Evangelista ◽

Jessica Audrey Feijó Corrêa ◽

João Vitor Garcia dos Santos ◽

Eduardo Henrique Custódio Matté ◽

Mônica Moura Milek ◽

...

Keyword(s):

Antimicrobial Activity ◽

Lactic Acid ◽

Antimicrobial Resistance ◽

Lactic Acid Bacteria ◽

Type Species ◽

Feed Additives ◽

Poultry Feed ◽

Content Type ◽

Link Type

The genus Salmonella is closely associated with foodborne outbreaks and animal diseases, and reports of antimicrobial resistance in Salmonella species are frequent. Several alternatives have been developed to control this pathogen, such as cell-free supernatants (CFS). Our objective here was to evaluate the use of lactic acid bacteria (LAB) CFS against Salmonella in vitro. Seventeen strains of LAB were used to produce CFS, and their antimicrobial activity was screened towards six strains of Salmonella . In addition, CFS were also pH-neutralized and/or boiled. Those with the best results were lyophilized. MICs of lyophilized CFS were 11.25–22.5 g l–1. Freeze-dried CFS were also used to supplement swine and poultry feed (11.25 g kg–1) and in vitro simulated digestion of both species was performed, with Salmonella contamination of 5×106 and 2×105 c.f.u. g−1 of swine and poultry feed, respectively. In the antimicrobial screening, all acidic CFS were able to inhibit the growth of Salmonella . After pH neutralization, Lactobacillus acidophilus Llorente, Limosilactobacillus fermentum CCT 1629, Lactiplantibacillus plantarum PUCPR44, Limosilactobacillus reuteri BioGaia, Lacticaseibacillus rhamnosus ATCC 7469 and Pediococcus pentosaceus UM116 CFS were the only strains that partially maintained their antimicrobial activity and, therefore, were chosen for lyophilization. In the simulated swine digestion, Salmonella counts were reduced ≥1.78 log c.f.u. g–1 in the digesta containing either of the CFS. In the chicken simulation, a significant reduction was obtained with all CFS used (average reduction of 0.59±0.01 log c.f.u. ml–1). In general, the lyophilized CFS of L. fermentum CCT 1629, L. rhamnosus ATCC 7469 and L. acidophilus Llorente presented better antimicrobial activity. In conclusion, CFS show potential as feed additives to control Salmonella in animal production and may be an alternative to the use of antibiotics, minimizing problems related to antimicrobial resistance.

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Genomic evolution and local epidemiology of Klebsiella pneumoniae from a major hospital in Beijing, China, over a 15 year period: dissemination of known and novel high-risk clones

Microbial Genomics ◽

10.1099/mgen.0.000520 ◽

2021 ◽

Author(s):

Mattia Palmieri ◽

Kelly L. Wyres ◽

Caroline Mirande ◽

Zhao Qiang ◽

Ye Liyan ◽

...

Keyword(s):

High Risk ◽

Klebsiella Pneumoniae ◽

Type Species ◽

Treatment Options ◽

Multidrug Resistant ◽

Virulence Plasmid ◽

Content Type ◽

Origin And Evolution ◽

Link Type ◽

Beijing China

Klebsiella pneumoniae is a frequent cause of nosocomial and severe community-acquired infections. Multidrug-resistant (MDR) and hypervirulent (hv) strains represent major threats, and tracking their emergence, evolution and the emerging convergence of MDR and hv traits is of major importance. We employed whole-genome sequencing (WGS) to study the evolution and epidemiology of a large longitudinal collection of clinical K. pneumoniae isolates from the H301 hospital in Beijing, China. Overall, the population was highly diverse, although some clones were predominant. Strains belonging to clonal group (CG) 258 were dominant, and represented the majority of carbapenemase-producers. While CG258 strains showed high diversity, one clone, ST11-KL47, represented the majority of isolates, and was highly associated with the KPC-2 carbapenemase and several virulence factors, including a virulence plasmid. The second dominant clone was CG23, which is the major hv clone globally. While it is usually susceptible to multiple antibiotics, we found some isolates harbouring MDR plasmids encoding for ESBLs and carbapenemases. We also reported the local emergence of a recently described high-risk clone, ST383. Conversely to strains belonging to CG258, which are usually associated to KPC-2, ST383 strains seem to readily acquire carbapenemases of different types. Moreover, we found several ST383 strains carrying the hypervirulence plasmid. Overall, we detected about 5 % of simultaneous carriage of AMR genes (ESBLs or carbapenemases) and hypervirulence genes. Tracking the emergence and evolution of such strains, causing severe infections with limited treatment options, is fundamental in order to understand their origin and evolution and to limit their spread. This article contains data hosted by Microreact.

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Lentzea tibetensis sp. nov., a novel Actinobacterium with antimicrobial activity isolated from soil of the Qinghai–Tibet Plateau

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijsem.0.004976 ◽

2021 ◽

Vol 71 (8) ◽

Author(s):

Jiao Huang ◽

Ying Huang

Keyword(s):

Antimicrobial Activity ◽

Type Species ◽

Sequence Similarity ◽

Tibet Plateau ◽

Rrna Gene ◽

Content Type ◽

Link Type ◽

Genome Wide ◽

Pr China ◽

Qinghai Tibet Plateau

A novel filamentous Actinobacterium, designated strain FXJ1.1311T, was isolated from soil collected in Ngari (Ali) Prefecture, Qinghai-Tibet Plateau, western PR China. The strain showed antimicrobial activity against Gram-positive bacteria and Fusarium oxysporum. Results of phylogenetic analysis based on 16S rRNA gene sequences indicated that strain FXJ1.1311T belonged to the genus Lentzea and showed the highest sequence similarity to Lentzea guizhouensis DHS C013T (98.04%). Morphological and chemotaxonomic characteristics supported its assignment to the genus Lentzea . The genome-wide average nucleotide identity between strain FXJ1.1311T and L. guizhouensis DHS C013T as well as other Lentzea type strains was <82.2 %. Strain FXJ1.1311T also formed a monophyletic line distinct from the known Lentzea species in the phylogenomic tree. In addition, physiological and chemotaxonomic characteristics allowed phenotypic differentiation of the novel strain from L. guizhouensis . Based on the evidence presented here, strain FXJ1.1311T represents a novel species of the genus Lentzea , for which the name Lentzea tibetensis sp. nov. is proposed. The type strain is FXJ1.1311T (=CGMCC 4.7383T=DSM 104975T).

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Prospective multi-center evaluation on risk factors, clinical characteristics and outcomes due to carbapenem resistance in Acinetobacter baumannii complex bacteraemia: experience from the Chinese Antimicrobial Resistance Surveillance of Nosocomial Infections (CARES) Network

Journal of Medical Microbiology ◽

10.1099/jmm.0.001222 ◽

2020 ◽

Vol 69 (7) ◽

pp. 949-959

Author(s):

Yudong Liu ◽

Qi Wang ◽

Chunjiang Zhao ◽

Hongbin Chen ◽

Henan Li ◽

...

Keyword(s):

Risk Factors ◽

Acinetobacter Baumannii ◽

Endotracheal Intubation ◽

Type Species ◽

Clinical Characteristics ◽

Carbapenem Resistance ◽

Male Gender ◽

Content Type ◽

Link Type ◽

All Cause Mortality

Introduction. Increasing evidence demonstrates unfavourable outcomes in bloodstream infections (BSI) due to the carbapenem-resistant Acinetobacter baumannii complex (CRAB). Aim. To investigate the differences in risk factors, clinical characteristics and outcomes in patients with A. baumannii complex BSI stratified by carbapenem resistance, a prospective multi-center study was conducted. Methodology. Information was collected in a predefined form. A total of 317 cases was included for comparison between CRAB BSI vs. carbapenem-susceptible A. baumannii complex (CSAB) BSI. Among these cases, 229 cases were defined as CRAB BSI and 88 cases as CSAB BSI. Results. Univariable analysis showed that male gender, underlying neurologic disease, prior carbapenems exposure, intensive care unit (ICU) stay, presence of central venous catheter, endotracheal intubation, tracheotomy, Foley catheter, nasogastric intubation, lower respiratory tract infections and catheter-related infections were more prevalent in CRAB BSI. Only male gender, prior carbapenems exposure and presence of endotracheal intubation persisted as independent risk factors for acquiring CRAB BSI. Patients with CRAB BSI displayed unfavourable outcomes characterized by failure of pathogen clearance, continuous fever, disease aggravation and higher incidence of 30-day all-cause mortality. Multivariate analysis demonstrated carbapenem resistance as an independent risk factor for 30-day all-cause mortality. Conclusion. Our findings reveal the epidemiological differences between CRAB BSI and CSAB BSI in a Chinese cohort. Our data suggest that carbapenem resistance has a significant impact on mortality for patients with A. baumannii complex BSI, further strengthening the importance of active prevention and control strategies for the spread of CRAB in Chinese hospitals.

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Molecular docking, dynamics and free energy analyses of Acinetobacter baumannii OXA class enzymes with carbapenems investigating their hydrolytic mechanisms

Journal of Medical Microbiology ◽

10.1099/jmm.0.001233 ◽

2020 ◽

Vol 69 (8) ◽

pp. 1062-1078

Author(s):

Balajee Ramachandran ◽

Jeyaraman Jeyakanthan ◽

Bruno S. Lopes

Keyword(s):

Free Energy ◽

Acinetobacter Baumannii ◽

Type Species ◽

Three Dimensional ◽

World Health ◽

Phenotypic Data ◽

Content Type ◽

Beta Lactamases ◽

Link Type ◽

Class D

Introduction. Acinetobacter baumannii is a critical priority pathogen listed by the World Health Organization due to increasing levels of resistance to carbapenem classes of antibiotics. It causes wound and other nosocomial infections, which can be life-threatening. Hence, there is an urgent need for the development of new classes of antibiotics. Aim. To study the interaction of carabapenems with class D beta-lactamases (oxacillinases) and analyse drug resistance by studying enzyme–substrate complexes using modelling approaches as a means of establishing correlations with the phenotypic data. Methodology. The three-dimensional structures of carbapenems (doripenem, ertapenem, imipenem and meropenem) were obtained from DrugBank and screened against class D beta-lactamases. Further, the study was extended with their variants. The variants’ structure was homology-modelled using the Schrödinger Prime module (Schrödinger LLC, NY, USA). Results. The first discovered intrinsic beta-lactamase of Acinetobacter baumannii , OXA-51, had a binding energy value of −40.984 kcal mol−1, whereas other OXA-51 variants, such as OXA-64, OXA-110 and OXA-111, have values of −60.638, –66.756 and −67.751 kcal mol−1, respectively. The free energy values of OXA-51 variants produced better results than those of other groups. Conclusions. Imipenem and meropenem showed MIC values of 2 and 8 µg ml−1, respectively against OXA-51 in earlier studies, indicating that these are the most effective drugs for treatment of A. baumannii infection. According to our results, OXA-51 is an active enzyme that shows better interactions and is capable of hydrolyzing carbapenems. When correlating the hydrogen-bonding interaction with MIC values, the predicted results are in good agreement and might provide initial insights into performing similar studies related to OXA variants or other antibiotic–enzyme-based studies.

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Repurposing bioactive compounds for treating multidrug-resistant pathogens

Journal of Medical Microbiology ◽

10.1099/jmm.0.001172 ◽

2020 ◽

Vol 69 (6) ◽

pp. 881-894 ◽

Cited By ~ 3

Author(s):

Nicholas A. Hummell ◽

Natalia V. Kirienko

Keyword(s):

Antimicrobial Activity ◽

Bioactive Compounds ◽

Mammalian Cells ◽

Type Species ◽

Antimicrobial Properties ◽

Drug Repurposing ◽

Virulence Determinants ◽

Content Type ◽

C Elegans ◽

Link Type

Introduction. Antimicrobial development is being outpaced by the rising rate of antimicrobial resistance in the developing and industrialized world. Drug repurposing, where novel antibacterial functions can be found for known molecular entities, reduces drug development costs, reduces regulatory hurdles, and increases rate of success. Aim. We sought to characterize the antimicrobial properties of five known bioactives (DMAQ-B1, carboplatin, oxaliplatin, CD437 and PSB-069) that were discovered in a high-throughput phenotypic screen for hits that extend Caenorhabditis elegans survival during exposure to Pseudomonas aeruginosa PA14. Methodology. c.f.u. assays, biofilm staining and fluorescence microscopy were used to assay the compounds' effect on various virulence determinants. Checkerboard assays were used to assess synergy between compounds and conventional antimicrobials. C. elegans-based assays were used to test whether the compounds could also rescue against Enterococcus faecalis and Staphyloccus aureus. Finally, toxicity was assessed in C. elegans and mammalian cells. Results. Four of the compounds rescued C. elegans from a second bacterial pathogen and two of them (DMAQ-B1, a naturally occurring insulin mimetic, and CD437, an agonist of the retinoic acid receptor) rescued against all three. The platinum complexes displayed increased antimicrobial activity against P. aeruginosa . Of the molecules tested, only CD437 showed slight synergy with ampicillin. The two most effective compounds, DMAQ-B1 and CD437, showed toxicity to mammalian cells. Conclusion. Although these compounds' potential for repurposing is limited by their toxicity, our results contribute to this growing field and provide a simple road map for using C. elegans for preliminary testing of known bioactive compounds with predicted antimicrobial activity.

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Delivery of antibacterial silver nanoclusters to Pseudomonas aeruginosa using species-specific DNA aptamers

Journal of Medical Microbiology ◽

10.1099/jmm.0.001174 ◽

2020 ◽

Vol 69 (4) ◽

pp. 640-652 ◽

Cited By ~ 3

Author(s):

Jennifer Soundy ◽

Darren Day

Keyword(s):

Pseudomonas Aeruginosa ◽

Antimicrobial Activity ◽

Type Species ◽

Galleria Mellonella ◽

Host Cells ◽

Silver Nanoclusters ◽

Bacterial Cells ◽

Content Type ◽

Link Type

Introduction. The use of silver as an antimicrobial therapeutic is limited by its toxicity to host cells compared with that required to kill bacterial pathogens. Aim. To use aptamer targeting of DNA scaffolded silver nanoclusters as an antimicrobial agent for treating Pseudomonas aeruginosa infections. Methodology. Antimicrobial activity was assessed in planktonic cultures and in vivo using an invertebrate model of infection. Results. The aptamer conjugates that we call aptabiotics have potent antimicrobial activity. Targeted silver nanoclusters were more effective at killing P. aeruginosa than the equivalent quantity of untargeted silver nanoclusters. The aptabiotics have an IC50 of 1.3–2.6 µM against planktonically grown bacteria. Propidium iodide staining showed that they rapidly depolarize bacterial cells to kill approximately 50 % of the population within 10 min following treatment. In vivo testing in the Galleria mellonella model of infection prolonged survival from an otherwise lethal infection. Conclusion. Using P. aeruginosa as a model, we show that targeting of DNA-scaffolded silver nanoclusters with an aptamer has effective fast-acting antimicrobial activity in vitro and in an in vivo animal model.

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A comparative study of pan-genome methods for microbial organisms: Acinetobacter baumannii pan-genome reveals structural variation in antimicrobial resistance-carrying plasmids

Microbial Genomics ◽

10.1099/mgen.0.000690 ◽

2021 ◽

Vol 7 (11) ◽

Author(s):

Aysun Urhan ◽

Thomas Abeel

Keyword(s):

Acinetobacter Baumannii ◽

Type Species ◽

Variant Calling ◽

Reference Sequence ◽

Beta Lactam ◽

Final Size ◽

Content Type ◽

Pan Genome ◽

Link Type ◽

Microbial Organisms

Microbial organisms have diverse populations, where using a single linear reference sequence in comparative studies introduces reference-bias in downstream analyses, and leads to a failure to account for variability in the population. Recently, pan-genome graphs have emerged as an alternative to the traditional linear reference with many successful applications and a rapid increase in the number of methods available in the literature. Despite this enthusiasm, there has been no attempt at exploring these graph construction methods in depth, demonstrating their practical use. In this study, we aim to develop a general guide to help researchers who may want to incorporate pan-genomes in their analyses of microbial organisms. We evaluated the state-of-the art pan-genome construction tools to model a collection of 70 Acinetobacter baumannii strains. Our results suggest that all tools produced pan-genome graphs conforming to our expectations based on previous literature, and that their approach to homologue detection is likely to be the most influential in determining the final size and complexity of the pan-genome. The graphs overlapped most in the core pan-genome content while the cloud genes varied significantly among tools. We propose an alternative approach for pan-genome construction by combining two of the tools, Panaroo and Ptolemy, to further exploit them in downstream analyses, and demonstrate the effectiveness of our pipeline for structural variant calling in beta-lactam resistance genes in the same set of A. baumannii isolates, identifying various transposon structures for carbapenem resistance in chromosome, as well as plasmids. We identify a novel plasmid structure in two multidrug-resistant clinical isolates that had previously been studied, and which could be important for their resistance phenotypes.

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Worldwide distribution and environmental origin of the Adelaide imipenemase (AIM-1), a potent carbapenemase in Pseudomonas aeruginosa

Microbial Genomics ◽

10.1099/mgen.0.000715 ◽

2021 ◽

Vol 7 (12) ◽

Author(s):

Anteneh Amsalu ◽

Sylvia A. Sapula ◽

Jonathan J. Whittall ◽

Bradley J. Hart ◽

Jan M. Bell ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Type Species ◽

Treatment Options ◽

Amino Acid Sequences ◽

Whole Genome Sequence ◽

Resistant Bacteria ◽

Metagenomic Sequencing ◽

Content Type ◽

Link Type ◽

Wastewater Samples

Carbapenems are potent broad-spectrum β-lactam antibiotics reserved for the treatment of serious infections caused by multidrug-resistant bacteria such as Pseudomonas aeruginosa . The surge in P. aeruginosa resistant to carbapenems is an urgent threat, as very few treatment options remain. Resistance to carbapenems is predominantly due to the presence of carbapenemase enzymes. The assessment of 147 P . aeruginosa isolates revealed that 32 isolates were carbapenem non-wild-type. These isolates were screened for carbapenem resistance genes using PCR. One isolate from wastewater contained the Adelaide imipenemase gene (bla AIM-1) and was compared phenotypically with a highly carbapenem-resistant clinical isolate containing the bla AIM-1 gene. A further investigation of wastewater samples from various local healthcare and non-healthcare sources as well as river water, using probe-based qPCR, revealed the presence of the bla AIM-1 gene in all the samples analysed. The widespread occurrence of bla AIM-1 throughout Adelaide hinted at the possibility of more generally extensive spread of this gene than originally thought. A blast search revealed the presence of the bla AIM-1 gene in Asia, North America and Europe. To elucidate the identity of the organism(s) carrying the bla AIM-1 gene, shotgun metagenomic sequencing was conducted on three wastewater samples from different locations. Comparison of these nucleotide sequences with a whole-genome sequence of a P. aeruginosa isolate revealed that, unlike the genetic environment and arrangement in P. aeruginosa , the bla AIM-1 gene was not carried as part of any mobile genetic elements. A phylogenetic tree constructed with the deduced amino acid sequences of AIM-1 suggested that the potential origin of the bla AIM-1 gene in P. aeruginosa might be the non-pathogenic environmental organism, Pseudoxanthomonas mexicana .

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Effect of pH on the antimicrobial activity of the macrophage metabolite itaconate

Microbiology ◽

10.1099/mic.0.001050 ◽

2021 ◽

Vol 167 (5) ◽

Author(s):

Dustin Duncan ◽

Andréanne Lupien ◽

Marcel A. Behr ◽

Karine Auclair

Keyword(s):

Antimicrobial Activity ◽

Type Species ◽

Antimicrobial Effect ◽

Bacterial Strains ◽

Content Type ◽

Biologically Relevant ◽

Link Type ◽

Activity Measurements ◽

Serovar Typhimurium ◽

The Media

The production of itaconate by macrophages was only discovered in 2011. An increasing number of studies have since revealed essential biological functions for this small molecule, ranging from antimicrobial to immunomodulator. The antibacterial role of itaconate has however been questioned because the estimated concentration of itaconate in macrophages (low-millimolar) is lower than the minimum inhibitory concentration (MIC) of itaconate reported for several bacterial strains (low-to-mid-millimolar). We note that some of these investigations have tended to ignore the high acidity of this small diacid (pKas 3.85 and 5.45), thereby potentially biassing activity measurements. We measured the MIC of itaconate in Escherichia coli (not known to metabolize itaconate) and in Salmonella enterica serovar Typhimurium (known to metabolize itaconate) at varying pH values to probe the effect that pH has on itaconate toxicity. Herein, we demonstrate that the antimicrobial effect of itaconate is dependent upon the pH of the media and that itaconate does have antimicrobial activity at biologically relevant pH and concentrations. Under nutrient-poor conditions, the antimicrobial activity of itaconate in both E. coli and S. Typhimurium increased approximately 200-fold when the pH was dropped by one unit, whereas itaconate was not found to be toxic under nutrient rich conditions. Our results also reveal that the activity of itaconate is synergistic with acidity, yet is not a function of increased permeability with protonation. Similar experiments performed with succinate (a pKa-matched diacid) yielded drastically different results, consistent with a target-based mechanism of action for itaconate. Overall, our work shows the importance of controlling the pH when performing experiments with itaconic acid.

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